802.11h, Channelfly and the 2.4 Ghz band

ChannelFly uses 802.11h to notify the client that the channel is being changed. We seem to be having some issues with this, even with modern drivers and wifi cards (Intel Ultimate-N 6300 AGN) with latest drivers. Does the standard mandate support only for DFS channels, or does it apply to all channels including the ones in the 2.4 Ghz band. The Intel cards claim support for this standard yet we don't see it working consistently.